How do i know if my rear end is going out?

I think that my rear end is going out. The gears whine at higher speeds, which is normal but at low speeds you can hear that the gears make noise in certain spots. It is like there is a spot on one of the gears "bad" cause it makes noise like wurr wurr wurr. it has done that since i got it back from getting the 3.73s. i have about 2-3000 miles on the gears. i have noticed that at about 55+ it had a little vibration. on the way to drop the car off to get my stall put in, i was going about 45-55 and noticed that the car was rocking a little like a wobble. i thought it was the road but on he highway it did it again. the tires were all good i checked the pressures before leaving. what would cause the car to wobble? is my rearend going out?

Not sure man but my motto is if it ain't broke don't fix it. My old 10 bolt had 4:10s in and absolutely screamed. I was nervous bout it as you are and picked up a Strange 12 bolt. The guy that bought my 10 bolt had a cammed SS w/Mickey Thompsons and made like at least 30 passes on it and it never broke. He later bought a nine inch cause he figured it was on borrowed time as well. My 12 bolt now makes all kinds of noise as well. I just ignore it. My .02. May wanna have a Tranny shop pull the cover off and inspect the backlash/pinion depth etc if it really worries you tho.